1. Field of the Invention
The present invention is generally related to a method of fabricating interconnections including a multi-layer metal film stack, particularly, to an improvement in corrosion and heat resistances of interconnections.
2. Description of the Related Art
TFT (thin film transistor) apparatuses, such as LCDs (liquid crystal displays), require low resistivity interconnections with high corrosion and heat resistances. A technique for fabricating such interconnections is disclosed in Japanese Patent Application No. Jp-A-Heisei 8-62628. The disclosed technique involves forming a refractory metal film, oxidizing the surface of the refractory metal film, forming an aluminum film on the oxidized surface, oxidizing the upper surface of the aluminum film, forming another refractory metal film on the oxidized surface of the aluminum film to complete a film stack, patterning the film stack, and oxidizing sides of the film stack. The oxides effectively avoids the aluminum film being corroded by stripping agent for stripping off resist patterns used as a mask.
Japanese Patent Application No. P2000-26335A discloses an interconnections structure composed of an aluminum film sandwiched by a pair of refractory metal films. Oxygen including aluminum films are disposed between the aluminum film and refractory metal films to prevent thermally induced counter diffusion between the aluminum film and refractory metal films.
Japanese Patent Application No. P2002-198360 discloses an etching technique for etching a structure including a silicon layer, and an aluminum layer disposed on the upper surface of the silicon layer. The disclosed etching technique involves etching the aluminum layer with Cl2 gas and H2 gas, and etching the silicon layer with SF6 gas, and HCl gas and He gas. The document also discloses the use of Cl2 gas in place of the HCl gas.
Japanese Patent Application No. P2002-90774A discloses a LCD fabrication process to reduce deterioration of liquid crystal within cells caused by pollution with material of gate electrodes. The disclosed process involves successively depositing an aluminum layer and a molybdenum layer, partially etching the molybdenum layer in an effective display region of the display panel, and oxidizing the aluminum layer in the effective display region through an anodization technique to complete the gate electrodes.
Japanese Patent Application No. 2000-252473 discloses a TFT structure for achieving low resistivity ohmic contact onto gate electrodes. The disclosed TFT structure is composed of gate electrodes including first through third metal layers, the first metal layer being formed of refractory metal such as Ta, Hf, Nb, and Zr, the second metal layer being formed of low resistivity metal such as Al, Ti, Cu, Cr, W, and Mo, and the third metal layer being formed of refractory metal such as Ta, Hf, Nb, and Zr.